System and method for controlling ventilation system based upon humidity detection

ABSTRACT

A system and method for controlling activation and deactivation of an exhaust system for ventilating an enclosed space, such as a bathroom. The system includes a humidity sensor, a memory element, and a processing element. The sensor measures a humidity value in the space, and the memory element stores that value along with a series of previously measured humidity values. The memory also stores a look-up table which specifies activation and deactivation criteria for the exhaust system based on the measured humidity value and a normal humidity value. The processing element calculates the normal humidity value based on a weighted average of the stored series of humidity values, consults the look-up table, and controls the exhaust system as specified by the look-up table. The measured humidity value is added to the stored series of values at a first interval, and the normal humidity value is re-calculated at a second interval.

FIELD

The present invention relates to systems and methods for ventilatingenclosed spaces, and more particularly, to a system and method forcontrolling activation and deactivation of an exhaust system forventilating an enclosed space, such as a bathroom, based on a relativehumidity level.

BACKGROUND

Ventilation systems are often used to ventilate enclosed spaces, such asby removing humid air from bathrooms. The simplest ventilation systemsare manually switched on and off by an occupant of the space. Moresophisticated systems employ a sensor to measure an actual humiditylevel in the space, compare the measured actual humidity level to astored threshold humidity level, and automatically control activationand deactivation of an exhaust system based on whether the actualhumidity level exceeds the threshold humidity level. The exhaust systemremains activated until the actual humidity level falls below thethreshold humidity level or times out.

This background discussion is intended to provide information related tothe present invention which is not necessarily prior art.

SUMMARY

Embodiments of the present invention solve the above-described and otherproblems and limitations by providing a system and method forcontrolling activation and deactivation of an exhaust system forventilating an enclosed space based on a relative humidity level. Ratherthan blindly operate the ventilation system continuously or for apre-determined interval, the present invention smartly controlsoperation of the ventilation system based on the relative humidityvalue.

In a first embodiment of the present invention, a system is provided forcontrolling activation and deactivation of an exhaust system forventilating an enclosed space. The system may broadly include a humiditysensor, a memory element, and a processing element. The humidity sensormay be configured to measure a humidity value in the enclosed space. Thememory element may be configured to receive and store the measuredhumidity value along with a series of previously measured humidityvalues, and to store a look-up table. The processing element may beconfigured to calculate a normal humidity value based on a weightedaverage of the stored series of previously measured humidity values, andto consult the look-up table which specifies activation and deactivationcriteria for the exhaust system based on the measured humidity value andthe normal humidity value, and to cause the exhaust system to activateor deactivate as specified by the look-up table.

Various implementations of the first embodiment may include any one ormore of the following additional features. The exhaust system mayinclude an exhaust fan for drawing air out of the enclosed space, amotor for driving the exhaust fan, and a grill for shielding access toan interior of the exhaust system. The enclosed space may be a bathroom,and the exhaust system may be installed in a ceiling of the bathroom orattic space. The humidity sensor may be positioned near the exhaustsystem, or the humidity sensor may be positioned remote from the exhaustsystem. The measured humidity value may be added to the series ofpreviously measured humidity values and stored in the memory element ata first interval of approximately between ten and thirty seconds, orapproximately between fifteen and twenty-five seconds. The normalhumidity value may be calculated based on the weighted average of theseries of previously measured humidity values stored in the memoryelement over a second interval of approximately between twenty and fortyseconds, or approximately thirty seconds. While the exhaust system isactivated, the normal humidity value may not be re-calculated. If theexhaust system remains activated for more than a time limit, theprocessing element may deactivate the exhaust system even if themeasured humidity value does not satisfy the deactivation criteriaspecified in the look-up table, and the system may reset by determininga new normal humidity value. The system may further include an occupancysensor configured to determine whether the enclosed space is occupied,and the processing element may be further configured to controlactivation and deactivation of the exhaust system only when the enclosedspace is occupied.

In a second embodiment of the present invention, a system is providedfor controlling activation and deactivation of an exhaust fan forventilating a bathroom. The system may broadly include a humiditysensor, a memory element, and a processing element. The humidity sensormay be configured to measure a humidity value in the bathroom. Thememory element may be configured to receive and store at a firstinterval of approximately between ten and thirty seconds the measuredhumidity value along with a series of previously measured humidityvalues, and to store a look-up table. The processing element may beconfigured to calculate a normal humidity value based on a weightedaverage of the series of previously measured humidity values stored inthe memory element over a second interval of between twenty and fortyseconds, and to consult the look-up table which specifies activation anddeactivation criteria for the exhaust fan based on the measured humidityvalue and the normal humidity value, and to cause the exhaust fan toactivate or deactivate as specified by the look-up table. This secondembodiment may further one or more additional features discussed inconnection with other embodiments.

In a third embodiment of the present invention, a method is provided forcontrolling activation and deactivation of an exhaust fan forventilating a bathroom. The method may broadly include the followingsteps. A humidity sensor may measure a humidity value in the bathroom.An electronic memory element may receive and store at a first intervalof approximately between ten and thirty seconds the measured humidityvalue along with a series of previously measured humidity values. Anelectronic processing element may calculate a normal humidity valuebased on a weighted average of the series of previously measuredhumidity values stored in the memory element over a second interval ofbetween twenty and forty seconds. The electronic processing element mayconsult a look-up table stored in the memory element which specifiesactivation and deactivation criteria for the exhaust fan based on themeasured humidity value and the normal humidity value. The electronicprocessing element may cause the exhaust fan to activate or deactivateas specified by the look-up table. This third embodiment may furtherinclude one or more additional features discussed in connection withother embodiments.

This summary is not intended to identify essential features of thepresent invention, and is not intended to be used to limit the scope ofthe claims. These and other aspects of the present invention aredescribed below in greater detail.

DRAWINGS

Embodiments of the present invention are described in detail below withreference to the attached drawing figures, wherein:

FIG. 1 is a depiction of an embodiment of a system for controlling anexhaust system based on a relative humidity level; and

FIG. 2 is a flowchart of steps involved in a method for controlling theexhaust system based on the relative humidity level.

The figures are not intended to limit the present invention to thespecific embodiments they depict. The drawings are not necessarily toscale.

DETAILED DESCRIPTION

The following detailed description of embodiments of the inventionreferences the accompanying figures. The embodiments are intended todescribe aspects of the invention in sufficient detail to enable thosewith ordinary skill in the art to practice the invention. Otherembodiments may be utilized and changes may be made without departingfrom the scope of the claims. The following description is, therefore,not limiting. The scope of the present invention is defined only by theappended claims, along with the full scope of equivalents to which suchclaims are entitled.

In this description, references to “one embodiment”, “an embodiment”, or“embodiments” mean that the feature or features referred to are includedin at least one embodiment of the invention. Separate references to “oneembodiment”, “an embodiment”, or “embodiments” in this description donot necessarily refer to the same embodiment and are not mutuallyexclusive unless so stated. Specifically, a feature, structure, act,etc. described in one embodiment may also be included in otherembodiments, but is not necessarily included. Thus, particularimplementations of the present invention can include a variety ofcombinations and/or integrations of the embodiments described herein.

Broadly characterized, the present invention provides a system andcorollary method for controlling activation and deactivation of anexhaust system for ventilating an enclosed space based on a relativehumidity value. The system monitors transient fluctuations in humidityvalues over a period time in order to determine a normal humidity valueat any particular time. The system then sets limits on normal levels andcalls for ventilation when a current humidity value exceeds theselimits. Thus, rather than blindly operate the ventilation systemcontinuously or for a pre-determined interval, the present inventionsmartly controls operation of the ventilation system based on relativehumidity values.

Referring to FIG. 1, an embodiment of the system 10 is shown in contextwith an exemplary exhaust system 12 for ventilating an enclosed space14, such as a bathroom. The exemplary exhaust system 12 may be installedin a ceiling 16 of the space 14, and may broadly comprise an exhaust fan18 for drawing air out of the space 14, a motor 20 for driving theexhaust fan 18, and a grill 22 for shielding an interior 23 of theexhaust system 12. In the illustrated embodiment, the fan 18 is notpositioned remote from the ceiling 16 or grill 22, and the grill 22therefore shields access to the fan 18. The principles of the presentinvention, however, are applicable to remotely located fans whereductwork corrects the grill to the remote fan. The system 10 may broadlycomprise one or more humidity sensors 30; an electronic memory element32; and an electronic processing element 34.

The one or more humidity sensors 30 may be configured to measure ahumidity value of the air in the space 14. The humidity sensor(s) 30 maybe mounted near to 30 a,30 b and/or remote from 30 c the exhaust system12. The electronic memory element 32 may be configured to receive andstore the measured humidity value along with a series of previouslymeasured humidity values, and to store a look-up table. The system 10may measure and/or store the humidity value continuously orperiodically, such as at a first interval of approximately between ten(10) and thirty (30) seconds, or approximately between fifteen (15) andtwenty-five (25) seconds, or approximately eighteen and seventy-fivehundredths (18.75) seconds.

The electronic processing element 34 may be configured to calculate anormal humidity value based on a weighted average of the stored seriesof previously measured humidity values, and to consult the look-up tablewhich specifies criteria for activation or deactivation of the exhaustfan 18 based on the measured humidity value and the calculated normalhumidity value, and to cause the exhaust fan 18 to activate ordeactivate as specified by the look-up table. In one implementation, theprocessing element 34 may calculate at a second interval, which may beapproximately between twenty (20) and forty (40) seconds, orapproximately thirty (30) seconds, the weighted average of the series ofpreviously measured humidity values as follows: AverageHumidity=(Average Humidity−(Average Humidity/32))+(Reading×32)). If thefirst interval between humidity measurements and/or storage is eighteenand seventy-five hundredths (18.75) seconds, then this algorithmproduces an averaging filter with a natural time constant (T) of 10minutes (i.e., 18.75 seconds×32). This filter may track to within fivepercent (5%) of a step value change in three T (3T), or thirty (30)minutes.

Thus, the system 10 may measure and/or store the actual humidity valueat the first interval (e.g., eighteen and seventy-five hundredths(18.75) seconds), and then calculate the weighted average of the storedseries of previous humidity values measured over the second interval(e.g., thirty (30) seconds) to determine the “normal” humidity value forthe space 14. In general, if the normal humidity value is X, and if themeasured actual humidity value, Y, is greater than the system “ON” setpoint, then the system 10 may activate the exhaust fan 18, and then ifthe measured humidity value drops below the system “OFF” set point, thesystem 10 may deactivate the exhaust fan 18. In one implementation, aslong as the exhaust fan 18 is activated, the system 10 may not updatethe normal humidity value (i.e., the normal relative humidity value istemporarily fixed).

An exemplary look-up table may be constructed substantially as follows.In this table, XX % may be a user-adjustable variable between thirtypercent (30%) and seventy percent (70%), wherein lower values may bringhumidity values closer to normal, while higher values may reduce therunning time of the exhaust fan 18.

Fan “ON” Average Humidity Range Condition Fan “OFF” Condition  0 ≦Average Humidity < 20 Reading ≧ Average (Avg. Hum. + 25) − 25 * (1 − XX%) Humidity + 25 20 ≦ Average Humidity < 25 Reading ≧ Average (Avg.Hum. + 22.5) − 22.5 * (1 − XX %) Humidity + 22.5 25 ≦ Average Humidity <30 Reading ≧ Average (Avg. Hum. + 20) − 20 * (1 − XX %) Humidity + 20 30≦ Average Humidity < 35 Reading ≧ Average (Avg. Hum. + 17.5) − 17.5 * (1− XX %) Humidity + 17.5 35 ≦ Average Humidity < 40 Reading ≧ Average(Avg. Hum. + 15) − 15 * (1 − XX %) Humidity + 15 40 ≦ Average Humidity <45 Reading ≧ Average (Avg. Hum. + 12.5) − 12.5 * (1 − XX %) Humidity +12.5 45 ≦ Average Humidity < 50 Reading ≧ Average (Avg. Hum. + 10) −10 * (1 − XX %) Humidity + 10 50 ≦ Average Humidity < 55 Reading ≧Average (Avg. Hum. + 7.5) − 7.5 * (1 − XX %) Humidity + 7.5 If 55 ≦Average Humidity Reading ≧ Average (Avg. Hum. + 2.5) Humidity + 5

In one implementation, if the exhaust fan 18 remains activated for morethan a time limit, such as approximately between two (2) and three (3)hours, or approximately two and one-half (2.5) hours, the exhaust fan 18may be deactivated and the system 10 may be reset even if the measuredhumidity value does not satisfy the deactivation criteria. This mayoccur when the exhaust system 12 is not capable of sufficiently reducingthe humidity level, which might happen, for example, if a window isopened and the space 14 is flushed with humid outside air. If thishappens, a new normal humidity value may be determined to reflect theabnormally high humidity value, and the process may proceed with the newnormal humidity value.

In one implementation, the system may further include a motion or othersensor 38 configured to determine whether the space 14 is occupied, andto consider the occupancy status when controlling the exhaust fan 18,such as by activating or continuing to activate the exhaust system 12only when the enclosed space is occupied.

Referring to FIG. 2, an embodiment of the method 110 for controllingactivation and deactivation of the exhaust system 12 for ventilating theenclosed space 14 is shown broadly comprising the following steps.Measuring with the humidity sensor 30 the humidity value in the space14, as shown in step 112. Receiving and storing in the electronic memoryelement 32 at the first interval the measured humidity value along withthe series of previously measured humidity values, as shown in 114.Calculating with the electronic processing element 34 the normalhumidity value based on the weighted average of the series of previouslymeasured humidity values stored in the memory element 32 over the secondinterval, as shown in 116. Consulting by the processing element 34 thelook-up table stored in the memory element 32 which specifies activationand deactivation criteria for the exhaust system 12 based on themeasured humidity value and the calculated normal humidity value, asshown in 118. Causing by the processing element 34 the exhaust system 12to activate or deactivate as specified by the look-up table, as shown in120.

Other features described with regard to the system 10 may similarlyapply to the method 110. For example, in one implementation, if theexhaust system 12 remains activated for more than the time limit, themethod 110 may further include deactivating by the processing element 34the exhaust system 12 even if the measured humidity value does notsatisfy the deactivation criteria specified in the look-up table, andresetting by the processing element 34 by calculating a new normalhumidity value, as shown in 122. Similarly, the method 110 may furtherinclude determining with the occupancy sensor 38 whether the space 14 isoccupied, and controlling by the processing element 34 activation anddeactivation of the exhaust system 12 only when the space 14 isoccupied, as shown in step 124.

Although the invention has been described with reference to the one ormore embodiments illustrated in the figures, it is understood thatequivalents may be employed and substitutions made herein withoutdeparting from the scope of the invention as recited in the claims.

Having thus described one or more embodiments of the invention, what isclaimed as new and desired to be protected by Letters Patent includesthe following:
 1. A system for controlling activation and deactivationof an exhaust system for ventilating an enclosed space, the systemcomprising: a humidity sensor configured to measure a humidity value inthe enclosed space; a memory element configured to receive and store themeasured humidity value along with a series of previously measuredhumidity values, and to store a look-up table; and a processing elementconfigured to calculate a normal humidity value based on a weightedaverage of the stored series of previously measured humidity values, andto consult the look-up table which specifies activation and deactivationcriteria for the exhaust system based on the measured humidity value andthe normal humidity value, and to cause the exhaust system to activateor deactivate as specified by the look-up table.
 2. The system as setforth in claim 1, the exhaust system including an exhaust fan fordrawing air out of the enclosed space, a motor for driving the exhaustfan, and a grill for shielding access to an interior of the exhaustsystem.
 3. The system as set forth in claim 1, wherein the enclosedspace is a bathroom, and the exhaust system is installed in a ceiling ofthe bathroom.
 4. The system as set forth in claim 1, wherein thehumidity sensor is positioned near the exhaust system.
 5. The system asset forth in claim 1, wherein the humidity sensor is positioned remotefrom the exhaust system.
 6. The system as set forth claim 1, wherein themeasured humidity value is added to the series of previously measuredhumidity values and stored in the memory element at a first interval ofbetween ten and thirty seconds.
 7. The system as set forth claim 1,wherein the measured humidity value is added to the series of previouslymeasured humidity values and stored in the memory element at a firstinterval of between fifteen and twenty-five seconds.
 8. The system asset forth in claim 1, wherein the normal humidity value is calculatedbased on the weighted average of the series of previously measuredhumidity values stored in the memory element over a second interval ofbetween twenty and forty seconds.
 9. The system as set forth in claim 8,wherein while the exhaust system is activated, the normal humidity valueis not re-calculated.
 10. The system as set forth in claim 1, whereinthe normal humidity value is calculated based on the weighted average ofthe series of previously measured humidity values stored in the memoryelement over a second interval of thirty seconds.
 11. The system as setforth in claim 1, wherein if the exhaust system remains activated formore than a time limit, the processing element deactivates the exhaustsystem even if the measured humidity value does not satisfy thedeactivation criteria specified in the look-up table, and the systemresets by determining a new normal humidity value.
 12. The system as setforth in claim 1, further including an occupancy sensor configured todetermine whether the enclosed space is occupied, and the processingelement is further configured to control activation and deactivation ofthe exhaust system only when the enclosed space is occupied.
 13. Asystem for controlling activation and deactivation of an exhaust fan forventilating a bathroom, the system comprising: a humidity sensorconfigured to measure a humidity value in the bathroom; a memory elementconfigured to receive and store at a first interval of between ten andthirty seconds the measured humidity value along with a series ofpreviously measured humidity values, and to store a look-up table; and aprocessing element configured to calculate a normal humidity value basedon a weighted average of the series of previously measured humidityvalues stored in the memory element over a second interval of betweentwenty and forty seconds, and to consult the look-up table whichspecifies activation and deactivation criteria for the exhaust fan basedon the measured humidity value and the normal humidity value, and tocause the exhaust fan to activate or deactivate as specified by thelook-up table.
 14. The system as set forth in claim 13, wherein whilethe exhaust fan is activated, the normal humidity value is notre-calculated.
 15. The system as set forth in claim 13, wherein if theexhaust fan remains activated for more than a time limit, the processingelement deactivates the exhaust fan even if the measured humidity valuedoes not satisfy the deactivation criteria specified in the look-uptable, and the system resets by determining a new normal humidity value.16. The system as set forth in claim 13, further including an occupancysensor configured to determine whether the bathroom is occupied, and theprocessing element is further configured to control activation anddeactivation of the exhaust fan only when the enclosed space isoccupied.
 17. A method for controlling activation and deactivation of anexhaust fan for ventilating a bathroom, the method comprising: measuringwith a humidity sensor a humidity value in the bathroom; receiving andstoring in an electronic memory element at a first interval of betweenten and thirty seconds the measured humidity value along with a seriesof previously measured humidity values; and calculating with anelectronic processing element a normal humidity value based on aweighted average of the series of previously measured humidity valuesstored in the electronic memory element over a second interval ofbetween twenty and forty seconds; consulting by the electronicprocessing element a look-up table stored in the electronic memoryelement which specifies activation and deactivation criteria for theexhaust fan based on the measured humidity value and the calculatednormal humidity value; and causing by the electronic processing elementthe exhaust fan to activate or deactivate as specified by the look-uptable.
 18. The method as set forth in claim 17, wherein while theexhaust fan is activated, the normal humidity value is notre-calculated.
 19. The method as set forth in claim 17, furtherincluding, if the exhaust system remains activated for more than a timelimit— deactivating by the electronic processing element the exhaust faneven if the measured humidity value does not satisfy the deactivationcriteria specified in the look-up table; and resetting by the electronicprocessing element by calculating a new normal humidity value.
 20. Themethod as set forth in claim 17, further including— determining with anoccupancy sensor whether the bathroom is occupied; and controlling bythe electronic processing element activation and deactivation of theexhaust fan only when the bathroom is occupied.